1. Field of the Invention
The present invention relates to method and apparatus for splicing together metal webs and, in particular, to such method and apparatus in which the metal webs are in part rolled.
2. Description of the Related Art
As a conventional metal webs splicing technique, there is known a technique in which a reduction roller is used to roll welded beads (Japanese Utility Model Application Laid-open (Jikkai) No. 62-179116).
Referring now to FIG. 13, there is shown a conventional splicing apparatus in which a roller 50 with projected portion 54 is used to reduce the thickness of a metal web 52 in part. That is, the roller 50 has a projected portion 54 existing successively in the outer periphery thereof and the metal web is held or fixed by a fixing jig 56 to a table 58 and after that it is rolled by the projected portion 54.
In FIG. 14, there is shown a conventional splicing method in which the projected portion 54 of the projection roller 50 is used to reduce a level difference in a spliced portion 60 between the two metal webs 52, 52 to improve the shape of the spliced portion so as to prevent centralization of stresses. The spliced portion 60 is situated on a back bar 62, is held or fixed by the fixing jigs shown in FIG. 14 or by a suction table 64, and is rolled by the projected portion 54 of the above-mentioned roller 50.
In FIG. 15, there is shown a method or rolling the end portion (the portion to be spliced) of the metal web 52 by use of the projected portion 54 of the roller 50 and, according to this method, the strip-shaped metal plate 52 is held or fixed by a stop jig 66 at the portion thereof adjacent to the passage of the roller 50 so as to prevent the metal web 52 from escaping out of position.
However, the above-mentioned metal webs splicing apparatus has been found disadvantageous in the following respects.
In other words, when a metal web to be rolled is thin and has a low rigidity, there are easily produced inconveniences such as constrictions and/or wrinkles. The production of the constrictions and wrinkles has a greatly ill effect on the flatness of the metal web as well as the precision of the shape thereof. Also, due to the fact that such constrictions and wrinkles are caused by the distortion of the portion to be rolled, if the pressure of rolling is increased, then the constrictions and wrinkles produced are further increased. This limits the magnitude of the rolling pressure, thereby lowering a working efficiency.
Also, in a conventional splicing method in which metal webs are butt-spliced together or lap-spliced together and the resultant spliced portion is rolled, if the metal webs are thin and have a low rigidity, constrictions and/or wrinkles are easy to occur in the spliced portion. When the spliced metal webs are carried or transferred over a large number of pass rollers successively in the following steps, stresses can be centralized on such constrictions and/or wrinkles existing on the spliced portion of the metal webs with the result that the spliced metal webs can be easily broken at such constrictions and/or wrinkles thereof.
In addition to the above, when such spliced portion is passed as a part of the metal web through a surface treatment step which is one of the following steps, there can be incurred various kinds of disadvantages.
For example, in a coating step of photosensitive layer in manufacturing a (lithographic) (planographic) printing plate, when the constrictions and/or wrinkles in the spliced portions are passed, through a coating device, the coating device must be shunted or moved aside in order to prevent against damage. Also, when the coating device is not shunted, the constrictions and/or wrinkles may swallow air bubbles therein, which has an ill effect on the state of the coated layer, resulting in a poor quality. Such constrictions and/or wrinkles caused by rolling the spliced portion in particular, occur remarkably when two or more thin metal webs each having a thickness of 0.1 mm to 0.2 mm are spliced together or when two or more metal webs having different thicknesses are spliced together.
Also, when the end portion (the portion to be spliced) of a metal web is to be previously rolled, if the width of the projected portion of the roller with projected portion is small with respect to a distance between the stop jig and the metal web end portion, then the metal web is very easy to escape out of place. Further, if the rolling pressure or downward pressure is decreased for prevention of escape of the metal web, then a working efficiency in rolling is disadvantageously lowered.
Moreover, in the conventional method and apparatus shown in FIGS. 13, 14 and 15, in a rolling process, when compared with the other portions of the metal web, in the spliced portion of the metal web, surface hardening occurs as well as the metal structure of the spliced portion is caused to change or deform. Such surface hardening and change or deformation of the metal structure give rise to various kinds of disadvantages when the spliced portion passes, as a part of the metal web, through a surface treatment step which is one of the following steps. For example, in a surface roughening step in a lithographic printing plate manufacturing process due to the fact that the spliced portion has been hardened by rolling, when the surface of the metal web is roughened mechanically by an abrasive or the like, the surface of the spliced portion may be hard to be roughened. Also, due to the fact that the metal structure of the spliced portion has been changed or deformed, when the metal web is surface roughened in an electrochemical manner, the spliced portion cannot be surface roughened sufficiently. Since the insufficiently surface roughened spliced portion provides a surface which is poor in wettability, when it passes through a coating step of such as a photosensitive layer or the like which is one of the following steps, the spliced portion may be in part short of the amount of application of coating solution and, the coating may be applied to such insufficient portion too much, which occurs just after the short application of the coating solution.
Also, if the above-mentioned excessive coating of the solution occurs, then the excessively coated surface of the spliced portion cannot be dried sufficiently and, therefore, when such coated surface of the spliced portions transferred over a pass roller or the like, the applied or coated solutions can be attached to the pass roller which has a greatly ill effect on the quality of the spliced metal webs.
In addition, since the projected portion of the rolling roller is transferred to the spliced portion, there is produced a level difference between the rolled portion and the unrolled portion. This level difference gives rise to various disadvantages in a surface treatment step which is one of the following steps. For example, in a coating step of a photosensitive layer in a planographic printing plate manufacturing process, when the level different section of the spliced portion is passed through, it swallows in air bubbles, which has an ill effect on the coated state of the metal web spliced portion, resulting in the deteriorated quality of the metal web. As the difference between the thickness of the metal web to be spliced is increased, the above-mentioned level difference in the spliced portion is increased.